A countertorque tail rotor is an integral aspect in the design of the majority of helicopters now in use. But there are numerous problems related to the design and operation of such tail rotors. Tail rotors are frequently mounted adjacent vertical fins which are provided for aircraft stability and with this configuration the helicopter rotor produces a transverse airflow which impinges the fin thereby reducing the thrust of the rotor and consuming additional power. The combination of the fin with the tail rotor further creates a disruptive air flow pattern which reduces the directional stability of the aircraft.
The size of a tail rotor is relatively limited and, to provide the required aerodynamic response, the tail rotor must be driven at a high angular velocity. When operating, the tail rotor generates high noise levels.
The vortices produced by a main rotor and a tail rotor interact in such a manner as to reduce the efficiency of the thrust created by the rotors while increasing the noise level as a result of the vortex interference.
Therefore, there exists a need for aircraft structure for use in conjunction with a helicopter rotor, either main rotor or tail rotor, for enhancing the rotor thrust, reducing the noise level and increasing directional stability while at the same time enclosing the rotor to prevent damage to the aircraft and injury to ground personnel.